Passerina caerulea sub species
Francisco Vega Reyes
2026-02-26
Subspecies of Blue Grosbeak and its potential use for Motus tags
This is an evaluation of the sub-species of Blue Grosbeak (Passerina caerulea) and its potential use as model species for Oaxacan Central Valleys. Most information comes from Birds Of the World https://birdsoftheworld.org/bow/species/blugrb1/cur/introduction and the publication from Storer and Zimmerman (1959) https://deepblue.lib.umich.edu/items/24824b17-6f43-4b56-9ad8-64da66786885.
Currently, 6 sub-species have been recognized, their infromation about morphometrics and distribution is summarized on this table:
| Sub especie | Region | Breeding | Wintering | Wing length mean (mm) | Wing length range | Tail length mean | Tail length range | Culmen length mean | Culmen length range | Body mass mean | Body mas range |
|---|---|---|---|---|---|---|---|---|---|---|---|
| caerulea | Eastern North America | Nebraska, Pensilvania, Texas, South Carolina | Greater antilles, E & S México, Panama | 88.36000 | 85 - 92 | 66.75333 | 63-73.5 | 12.44333 | 11.3 - 13.7 | NA | NA |
| interfusa | Western North America and México | Nevada, Colorado, Sonora, Chihuahua | Sonora, Jalisco and Valley of México | 89.70667 | 86.5 - 94 | 69.58667 | 66 - 75 | 12.24000 | 11.1 - 14 | NA | NA |
| salicaria | Californias | California and Baja California | Baja California Sur | 90.35000 | 88 - 94 | 71.00000 | 68 - 74.5 | 11.16000 | 10 - 11.8 | NA | NA |
| eurhyncha | México | México, Guanajuato, SLP, Northern? Oaxaca | NA | 94.17400 | 90 - 96 | 74.37000 | 70 - 80 | 12.94800 | 12.1 - 13.7 | NA | NA |
| eurhyncha | Oaxaca (n = 2) | Oaxaca (9 and 20mi Southeast Oaxaca) | NA | 95.50000 | 95-96 | 75.00000 | 74 - 76 | 13.30000 | 12.9 - 13.7 | NA | NA |
| chiapanensis | Chiapas (n = 7) | Chiapas | NA | 95.90000 | 93.5 - 98.5 | 76.60000 | 73 - 81 | 14.80000 | 14.5 - 15.1 | NA | NA |
| lazula | Central America | El Salvador, Costa Rica | NA | 91.11000 | 87.5 - 93 | 73.33000 | 68.5 - 77 | 14.09000 | 12.7 - 15.1 | NA | NA |
From these species, 2 or maybe 3 could be found in Oaxaca. These are caerulea, interfusa and eurhyncha.
| Sub especie | Region | Breeding | Wintering | Wing length mean (mm) | Wing length range | Tail length mean | Tail length range | Culmen length mean | Culmen length range | Body mass mean | Body mas range |
|---|---|---|---|---|---|---|---|---|---|---|---|
| caerulea | Eastern North America | Nebraska, Pensilvania, Texas, South Carolina | Greater antilles, E & S México, Panama | 88.36000 | 85 - 92 | 66.75333 | 63-73.5 | 12.44333 | 11.3 - 13.7 | NA | NA |
| interfusa | Western North America and México | Nevada, Colorado, Sonora, Chihuahua | Sonora, Jalisco and Valley of México | 89.70667 | 86.5 - 94 | 69.58667 | 66 - 75 | 12.24000 | 11.1 - 14 | NA | NA |
| eurhyncha | México | México, Guanajuato, SLP, Northern? Oaxaca | NA | 94.17400 | 90 - 96 | 74.37000 | 70 - 80 | 12.94800 | 12.1 - 13.7 | NA | NA |
| eurhyncha | Oaxaca (n = 2) | Oaxaca (9 and 20mi Southeast Oaxaca) | NA | 95.50000 | 95-96 | 75.00000 | 74 - 76 | 13.30000 | 12.9 - 13.7 | NA | NA |
Based on measurements we could tell appart individuals(?)
But the distribution of interfusa and eurhyncha for Oaxacan Central Valleys do not seem to overlap…
What does ebird say?
Blue Grosbeaks in Oaxaca
To evaluate the status and trends in detail I requested a status and trends passcode
“Tu clave de estatus y tendencias:
4inq4qjs1326”
Status and trends of Oaxaca Central Valley seem to show there are not a lot of migration happening on the Central Valleys (?):
But there are changes on relative abundances happening throughout the Central Valleys. Whether is because of individuals of interfusa arriving from México and the US of individuals of eurhyncha conducting local movements, we do not know.
BLUE GROSBEAKS AUDIOS
Here is information from the Macaulay library. I selected audios from each locality between June and August. All songs selected include at least 2 trill elements
NOTE: subspecie caerulea and and interfusa had longer songs than eurhyncha but were not included in these comparisons
The information of the audios goes as follows:
Oaxaca (eurhyncha)
Resident
NEW MEX, COLORADO(interfusa)
West Migrant
PEN, SOUTH CAROLINA (caerulea)
East migrant
